This gifs tutorial gives you the basics to make gifs from video files (cutting, croping, adding text...). The last example shows how to remove a (still) background to keep only the animated part of a video.

This transcribing piano rolls blog post explains how to transform a video of a piano roll performance into playable sheet music. MoviePy is used for the frame-by-frame analysis of the piano roll video. The last video is also edited with MoviePy:

Kapwing is an online video meme generator. Content creators use Kapwing to add text around their videos, which results in higher engagement / views on social media sites like Facebook. Kapwing’s creation process is powered by MoviePy! MoviePy is used to add the text, borders, and attribution directly to the uploaded videos.

Rincomcam is a camera which films surfers on the Californian beach of Point Rincon. At the end of each day it cuts together a video, puts it online, and tweets it. Everything is entirely automatized with Python.
MoviePy is used to add transitions, titles and music to the videos.

Videogrep is a python script written by Sam Lavigne, that goes through the subtitle tracks of movies and makes supercuts based on what it finds. For instance, here is an automatic supercut of every time the White House press secretary tells us what he can tell us:

This other post uses MoviePy to automatically cut together all the highlights of a soccer game, based on the fact that the crowd cheers louder when something interesting happens. All in under 30 lines of Python: